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Chapter 6 Options for Creating and Controlling Motion 157
FIGURE 6-23 A PWM signal
Think of PWM as flicking a light switch on and off. If you flick the light on and off fast
enough, the average of the dark and light makes it look like the light is on, but just
dimmer than if you leave it on. The same goes for a PWM signal to control a motor.
Instead of giving the motor its full-rated voltage, you flick the power on and off fast
enough that the average voltage is below what your power source gives you. For
example, if you have a 9V power source trying to drive a DC gearhead motor that
wants 3V to 6V, you could give it a pulse width at 50% of the time interval to equal a
voltage of 4.5V, and make the motor happy.
